Field of the Invention
The present disclosure relates to a wireless local area network (WLAN), and more particularly, to a method and apparatus for transmitting and receiving a high efficiency extended range single user physical protocol data unit (HE ER SU PPDU) in a WLAN.
Discussion of the Related Art
Although a frame transmission method as proposed below is applicable to various wireless communication systems, it will be described in the context of a WLAN system as an exemplary system to which the present disclosure is applicable.
Standards for WLAN technology have been developed as institute of electrical and electronics engineers (IEEE) 802.11 standards. IEEE 802.11a and b use an unlicensed band at 2.4 GHz or 5 GHz. IEEE 802.11b provides a transmission rate of 11 Mbps and IEEE 802.11a provides a transmission rate of 54 Mbps. IEEE 802.11g provides a transmission rate of 54 Mbps by applying orthogonal frequency division multiplexing (OFDM) at 2.4 GHz. IEEE 802.11n provides a transmission rate of 300 Mbps for four spatial streams by applying multiple input multiple output (MIMO)-OFDM. IEEE 802.11n supports a channel bandwidth of up to 40 MHz and, in this case, provides a transmission rate of 600 Mbps.
The above-described WLAN standards have evolved into IEEE 802.11ac that uses a bandwidth of up to 160 MHz and supports a transmission rate of up to 1 Gbits/s for 8 spatial streams and IEEE 802.11ax standards are under discussion.
A station (STA) conforming to the IEEE 802.11ax standard may be referred to as a high efficiency (HE) STA, and a physical layer radio frame used in a HE system may be referred to as a HE physical protocol data unit (HE PPDU).
Each element of a PPDU available in the HE system will be described below.
FIG. 1 is a view referred to for describing initial discussion of each element of a HE PPDU.
In IEEE 802.11ax, a legacy 1× symbol structure (3.2 μs) may be adopted for a part of a frame up to HE-SIGs (HE-SIG A and HE-SIG B), and a frame structure having a 4× symbol (12.8 μs) structure may be used for HE-preamble and Data of the frame, as illustrated in FIG. 1. Unless contradicting the following description, there is no problem with applying the present disclosure even though the above structure is changed.
An L-part may be configured as in a legacy wireless fidelity (Wi-Fi) system, and thus may include a legacy short training field (L-STF), a legacy long training field (L-LTF), and a legacy signal (L-SIG). Generally, the L-SIG preferably carries packet length information. A HE-part is a new part configured for the IEEE 802.11ax standard (High Efficiency). HE-SIGs (HE-SIG A and HE-SIG B) may be interposed between the L-part and a HE-STF, providing common control information and user-specific information. Specifically, the HE-SIGs may be configured separately as HE-SIG A for providing common control information and HE-SIG B for providing user-specific information.
Although the above HE PPDU format is applicable to all data transmissions of a STA, it is preferred to make a slight modification to the HE PPDU format according to a transmission state of the STA in order to increase system efficiency.